A holographic display method based on complex wavefront modulation using single spatial light modulator is proposed. The holographic display is achieved from complex wavefront encoded by double phase hologram. The modulated beam by single phase-only spatial light modulator passes through a 4f optical system to synthesize the expected complex modulated wavefront on the output plane, with a low-pass filter in the Fourier plane. The performance of holographic display is also improved by complex wavefront modulation, compared with the holographic display based on phase-only wavefront modulation. The proposed encoding and display technique is theoretically demonstrated, as well as validated in numerical simulations.
Aiming at the space target and two dominant background sources including the sun and earth-atmosphere system, their radiation models are established, and the background influence on the space target detection for the space-based infrared imaging system are discussed in the long wave infrared (8 to 14 μm) range. From the numerical calculation and analysis, we find that the earth-atmosphere system is the strongest background interference source and will form a big detection blind zone, followed by the sun, whose irradiance is about 1.6% of that from the earth-atmosphere system. Compared with these two intense radiations, the space target radiation acting on the space-based infrared detector is so weak that it may be submerged once the target appears in the earth-atmosphere or solar backgrounds. Thus, in order to reduce the influence of the background interferences, necessary measures must be taken to control the space-based infrared detector and its host platform in real time, such as adjusting the flight attitude, changing the detection angle, transferring operating orbit, and so on.
A kind of angular-multiplexing optical image encryption scheme is proposed based on Fresnel-transform holography and random amplitude encoding. By introducing reference plane waves with different incident angles in the output plane, we accomplished multiple-image encryption. To enhance the feasibility of the system and decrease the coding complexity and precision requirement for random-phase mask, random-amplitude masks were positioned in the input plane and inserted into the reference arm, and some digital manipulations were applied in the encryption and decryption procedure. We analyzed the encryption and decryption quality of the proposed encryption method together with the influence of different random number generators. Numerical simulation proved the validity of the proposed scheme.
An approach of in-situ measuring the complex response of a scene spatial light modulator which working in differential
state was presented by using an image of Ronchi grating substituted for a concrete one. Its principle and testing method
have been studied and a typical XGA2L11 spatial light modulator has been characterized. The scene image under
complicated background has been edge enhanced by mapping the measurement results, and the correlation results
showed that scene spatial modulator with the differential state can increase the SNR and PCE of correlation peak. The
way could be wholly applied in Vander Lugt Correlator and has very strong practicability and effectiveness.
A method for measuring refractive index of plate glass by joint transform correlative technique is given. In the one of two correlative light beams passing through the two correlative images of certain separation in input plane, a unknown refractive index and known thickness plate glass is inserted with a certainty angle (θ). Joint transform power spectrum (JPS) is recorded separately at the back focal plane of the lens by a CCD detector when Θ = 90° or Θ = 45°, the JPS is sent to the LCD on the input plane by the computer. Then two groups of correlative points will be recorded separately by the CCD detector. On the basis of the interval difference value between two groups of altered correlative points, the refractive index is calculated. Theory analysis and examination result are given.
Multiple synthetic discriminant function (SDF) filters has been verified to be a better strategy for distortion invariant optical pattern recognition, especially for the in-plane rotation invariant ones. However, how to select the training sets is very crucial for the filter’s validity. In this paper, referring to the Rayleigh criteria, the distortion tolerance of a single matched spatial filter (MSF) has been tested by using a digital-optical hybrid 4f correlation system. Experimental results are ±5° and ±8% for the rotation and scaling distortion tolerance, respectively. According to the results, an equal correlation peak phase-only SDF algorithm has been adopted to synthesize two SDF filters, in which the training set images have been correspondingly selected with 5° and 10° intervals. The SDF filter constructed with 10° interval training sets has demonstrated as good performance as that one with 5° interval, but with the advantage of reduction by half of the number of multiple SDF filters for 360° full-rotation, which indicated that the double of distortion tolerance selected as the interval of training images is more suitable for real-time correlator recognitions.
The design scheme and structure of a high accuracy temperature-controlling thermal radiation source for thermographic inspection are presented, the performance parameters of temperature-controlling thermal radiation source is given.
The principle of measuring passive incident laser beam's space direction by use of the PSD (photoelectric site detector) and structural design of system are presented. Theory and experiment show passive incident beam's space direction can be determined accurately and quickly.
A new method of measuring the PRN of CCD device is presented the PRN of CCD device can be determined quickly and accurately by this method, the effect of illuminance distribution nonuniformity on the measurement of CCD device PRN is eliminated.
The principle of determining passive incident laser beam's space direction by use of linear array CCD deice and structural design of the system are analyzed theory and experiment show passive incident laser beam's space direction can be determined accurately and quickly.